1. Field
The following disclosure relates to modified sulfur, preparation method thereof, preparation equipment thereof, and uses thereof. Particularly, the disclosure explains preparation equipment that produces modified sulfur having excellent properties with simpler and safer manner than traditional methods and can perform mass production of modified sulfur with serial manner. In addition, the modified sulfur according to the disclosure can be applied to various uses, for example anticorrosive materials, waterproofing materials and asphalt composite.
2. Background
Sulfur is a substance with 207° C. of flash point and 245° C. of self-ignition temperature, which can easily combust when being exposed to surface and contact with air and is likely to be generated during desulfurization process of crude oil or natural gas as well as in natural sulfur.
The sulfur in stable solid state has high strength when it has no defect in itself, but solid sulfur formed by cooling and solidification from liquid sulfur coexists as 3 types including orthorhombic, monoclinic and indeterminate form. This solidified sulfur has different coexistence ratio of the 3 type sulfur depending on its cooling condition, is likely to develop a defect in itself, and has brittleness that is easily broken. Thus, application range of pure sulfur is greatly limited.
Especially, sulfur is available in various construction materials but pure sulfur has limited application range due to the above mentioned characteristics. Concretely, for the sulfur material with a characteristic of brittle fracture as plastic deformation hardly develops and all of the force given to the material is used to destruction directly, it is an unstable material with characteristics similar to those of typical Portland concrete which is broken in a moment when power greater than yield strength is given.
In order to improve this disadvantage, various types of sulfur modifying agents are being reviewed. Particularly, dicyclopentadiene (DCPD) is known to have effects such as improvement of brittleness of the sulfur as well as good economic feasibility due to low price (New Uses of Sulfur-II, 1978, PP. 68-77, 1978).
However, the reaction between dicyclopentadiene and sulfur is difficult to control the polymerization itself, so has a risk to develop explosive exothermic reaction and its control is also difficult due to rapid increase of temperature and viscosity during the reaction process.
Especially, when the reaction exceeds appropriate polymerization range, a rubber-like phenomenon may occur, which specifically causes a damage of reactor used in the polymerization and is known to make commercial use of the sulfur modifying agent prepared from dicyclopentadiene modifying agent and sulfur remarkably difficult. In addition, the dicyclopentadiene and the sulfur have a lot of inefficient factors in their preparation and utilization due to supercooling after polymerization.
Besides regarding its application as anti-corrosive and waterproofing material, the anticorrosive corrosive treatment is needed for easily rusting or corrosive materials such as metals to play their role stably for long time and the waterproofing treatment is needed to prevent water leak of constructions including buildings from rainfall and a crack or lowering of durability in the construction itself. However, a lot of anti-corrosive and waterproofing materials have some problems to be improved including lower adhesiveness with target materials and complicated coating process.
The modified sulfur prepared by polymerization of sulfur and dicyclopentadiene-based modifier is usually a solid at room temperature and used after melting at over 120° C. Thus, in order to spray the modified sulfur to structures such as concrete or steel structure with a sprayer as for using it as an anti-corrosive material, there were some inconveniences in construction due to necessity for pretreatment at high temperature for melting it and additional meting device of the modified sulfur, so it has been difficult to use it widely in construction sites.
In addition, there was another considerable inconvenience that the sprayer should be cleaned and reheated for restart the work because the modified sulfur was solidified rapidly even in short term stopping within several minutes. These are very important problems restricting wide usage of anti-corrosive and waterproofing materials using the modified sulfur.
Furthermore regarding its application as a composite of asphalt, its temperature range applicable to asphalt road is very limitative because of problems including plastic deformation at high temperature and crack development at low temperature.
An effort to increase affinity between asphalt and copolymer by adding small amount of sulfur less than 5% to modified asphalt has been attempted and is used as a phase separation stabilizer. However, when using greater amount of sulfur over 10 parts by weight, its viscosity increases sharply from formation of gel, so there is a problem difficult to use it as a binder.
Although there have been a lot of studies on addition of large amount of sulfur to asphalt, they are not used widely because of gelation, a phenomenon of phase separation.
Thus, studies on asphalt composite that does not form gel and improve its property even in addition of large amount of sulfur have been progressed and traditional technologies relating to these are as follows.
U.S. Pat. No. 4,412,019 describes a modified asphalt composition adding 0˜20 parts by weight of sulfur to the asphalt in hydrogen treated butadiene-styrene block copolymer for preventing gelation. In addition, U.S. Pat. No. 5,756,566 shows a modified asphalt composition prepared by using 0.1˜5 parts by weight of antigelling agent against weight of asphalt in order to prepare asphalt-polymer compound that does not gelate.
In spite of progression of the above studies, there are still further needs for asphalt composition to improve antigelling property dramatically in adding large amount of sulfur to modified asphalt.
Besides for asphalt pavement, breakages of pavement such as plastic deformation and low temperature cracks occurs continuously under the influence of temperature rise in summer, explosive increase of traffic, and increase of congested areas.
In order to solve these problems, United States established and has operated PG (Performance Graded) test of asphalt as a national standard (ASTM D 6373) in 1990 and then has obtained encouraging effects that quality of the asphalt pavement is improved.
Accordingly traditionally small amount of modified sulfur as much as 5 parts by weight against 100 parts by weight of asphalt was added and when using it as over 10 parts by weight, there was a problem that the viscosity was increased sharply by gelation. Thus, it was general to add less than 20 parts by weight of modified sulfur against 100 parts by weight of asphalt and its cost was considerable due to necessity for addition of antigelling agent.
Moreover, the modified sulfur prepared by polymerization of dicyclopentadiene and sulfur according to the traditionally known manner is specifically solidified when left at room temperature, so has a problem that depression occurs during construction process. This becomes a problem particularly in construction process of polymer modified sulfur concrete with large volume not in the scale of laboratory level, which is a phenomenon developed by sharp temperature difference between the central part and the external part of concrete during cooling process of melted liquid sulfur deposited in a cast.
In order to this disadvantage, there have been a lot of studies and development efforts on property improved modified sulfur by adding various materials, there are still disadvantages including that the reaction control is difficult and figuration is impossible due to rapid solidification at room temperature.
Additionally, as damage of the preparing equipment from rubberization is another problem in traditional polymerization of dicyclopentadiene and sulfur, it is needed to develop a method for mass production of modified sulfur as well as property improvement of the modified sulfur for commercial mass production of the modified sulfur used in asphalt composition.